Fabrication of a pressure sensor uses ion implantation technology to form piezoresistive elements and highly doped conductive elements in a silicon layer. The piezoresistive elements are for stress sensing and the highly doped conductive elements are for reducing a conduct resistance between a metal layer and the silicon layer. A size of the pressure sensor is critical in applications including cardiovascular pressure measurements. Design of the pressure sensor requires consideration of trade-offs for reducing the size of the pressure sensor. A first preference is to have a thin membrane or diaphragm (for example, 3 microns thick or less) to increase the sensor output sensitivity. A second preference is to have a thick membrane or diaphragm (for example, 5 microns thick or more) to prevent leakage caused by a deep junction depth formed by a high dosage ion implantation (for example, greater than 1020 ions/cm3). The first preference contradicts the second preference. A first solution is to use a thick membrane with reduced sensor output sensitivity. A second solution is to use a thin membrane and to add doped poly-silicon or Epi-polysilicon on the thin membrane to form strain gauges. For example, U.S. Pat. No. 6,959,608 to Bly et al. discloses a pressure sensor having a one micron thick pressure sensing membrane and less than 0.1 micron thick piezoresistive strain gauges. A film stress however may be induced from the added poly-silicon or Epi-polysilicon. Therefore, to achieve both sensor output sensitivity and to reduce leakage, a third solution includes using a thin membrane and applying different ion implantation dosages on different pre-determined regions.